Integrated circuit (IC) devices and other electronic components are normally tested to verify the electrical function of the device and certain devices require high temperature burn-in testing to accelerate early life failures of these devices. The interconnection methods used to test these devices include permanent, semi-permanent, and techniques. The permanent and semi-permanent techniques that are typically used include soldering and wire bonding to provide a connection from the IC device to a substrate with fan out wiring or a metal lead frame package. The techniques include rigid and flexible probes that are used to connect the IC device to a substrate with fan out wiring or directly to the test equipment.
The permanent attachment techniques used for testing integrated circuit devices such as wire bonding to a leadframe of a plastic leaded chip carrier are typically used for devices that have low number of interconnections and the plastic leaded chip carrier package is relatively inexpensive. The device is tested through the wire bonds and leads of the plastic leaded chip carrier and plugged into a test socket. If the integrated circuit device is defective, the device and the plastic leaded chip carrier are discarded. The semi-permanent attachment techniques used for testing integrate circuit devices such as solder ball attachment to a ceramic or plastic pin grid array package are typically used for devices that have high number of interconnections and the pin grid array package is relatively expensive. The device is tested through the solder balls and the internal fan out wiring and pins of the pin grid array package that is plugged into a test socket. If the integrated circuit device is defective, the device can be removed from the pin grid array package by heating the solder balls to their melting point. The processing cost of heating and removing the chip is offset by the cost saving of reusing the pin grid array.
The most cost effective techniques for testing and burn-in of integrated circuit devices provide a direct interconnection between the pads on the device to a probe sockets that is hard wired to the test equipment. Contemporary probes for testing integrated circuits are expensive to fabricate and are easily damaged. The individual probes are typically attached to ring shaped printed circuit board and support cantilevered metal wires extending towards the center of the opening in the circuit board. Each probe wire must be aligned to a contact location on the integrated circuit device to be tested. The probe wires are generally fragile and easily deformed or damaged. This type of probe fixture is typically used for testing integrated circuit devices that have contact along the perimeter of the device. This type of probe cannot be used for testing integrated circuit devices that have high density are array contacts.
The prior art described below includes variety of different probe fixtures for bare testing IC chips. Although most of these probe fixtures use rigid protrusions to form the contact, only a few include a cup shaped geometry around the raised contact to contain the volume of the solder balls at high temperature. The Integral Rigid Test Probe is the only fixture that can be fabricated using an inexpensive epoxy glass laminate substrate with copper wiring and doesn't require additional proc essing steps for the IC chips to be tested. The ability to repair or replace and individual probe on the fixture is another unique feature to this approach.
U.S. Pat. No. 4,975,079 issued Dec. 4, 1990 to Beaman et al., is directed to fixtures for testing bare IC chips with solder balls on the I/O contacts at high temperatures for non-destructive burn-in. The fixture is manufactured on a multilayer ceramic substrate with an array of contact pads connected to the fanout wiring. An abrasive fabrication process is used to created raised probe contacts on the surface of the substrate. The raised probes are covered by a polymer material and cup shaped openings are ablated through the to expose the raised contacts. The inside of the cup shaped openings and the surface of the raised probes are covered with a conductive material. The geometry of the cup shaped opening and the surface of the raised probes are optimized to penetrate the solder balls attached to the IC chip contacts and contain the solder volume at high temperatures. The fabrication techniques used to create this probe fixture cannot be used to repair or replace individual probe contacts.
U.S. Pat No. 5,007,163 issued Apr. 16, 1991 to Pope et al., is directed to fixtures for testing bare IC chips with solder balls on the I/O contacts at high temperatures for non-destructive burn-in. The fixture is comprised of a fanout substrate that used liquid metal joints between the contacts on the surface of the substrate and the solder balls on the IC chip. The liquid metal is composed of two separate metals that form a cutectic mixture when joined together and the mixture is a liquid at room temperature. One of the metals is deposited on the contact pads of the fanout substrate and the other metal is deposited on the surface of the solder balls attached to the IC chip. This technique for testing IC chips requires additional processing steps for the IC chips to deposit the additional metal material to the solder balls on the IC chip before testing and to clean the cutectic metal mixture from the solder balls after testing is completed. These additional processing steps add to the cost of the IC chip and increase the potential for contamination of the IC solder balls with the cutectic metal mixture if not cleaned thoroughly.
U.S. Pat. No 5,172,050, issued Dec. 15, 1992 to Swapp is directed to fixtures for testing bare IC chips with solder balls on the I/O contacts. The fixture is manufactures from a silicon wafer or other semiconductor substrate material. The probe contacts are fabricated in the top surface of the substrate using micromachining techniques. Each prove contact is formed by etching a cavity into the substrate with a cantilevered beam extending into the center of the cavity, The fabrication techniques used to create this probe fixture cannot be used to repair or replace individual probe contacts. The geometry of the prove cavities are not useful for containing the plastic creep of the solder balls at high temperature. The minimum spacing and density of the probe contacts is limited by the need to use the space between the contacts for fanout wiring and the diameter of the cavities must be larger than the diameter of the solder balls to allow the cantilever beam contacts to flex.
U.S. Pat. No. 5,177,439, issued Jan. 5, 1993 to Liu et al., is directed to fixtures for testing bare IC chips. The fixture is manufactured from a silicon wafer or other substrate that is compatible with semiconductor processing. The substrate is chemically etched to produce a plurality of protrusions to match the I/O pattern on the bare IC chip. The protrusions are coated with a conductive material and connected to discrete conductive fanout wiring paths to allow connection to and external test system. The geometry of the protrusions for this fixture would not be compatible for high temperature testing of IC chips with solder balls on the I/O contact. The preferred geometry for high temperature testing of IC chips with solder balls is a small protrusion with a surrounding cup to contain the solder volume. The substrate used for fabrication of this probe fixture is limited to semiconductor wafers which are relatively expensive. The Integral Rigid Test Probe can be fabricated on a variety of inexpensive substrate with the fanout wiring.
U.S. Pat. No 5,207,585, issued May 4, 1993 to Byrnes et al., describes a thin interface pellicle probe for testing integrated circuit devices with solder balls. The probe structure described in this patent used metal rivets that are formed on a thin layer of polymer material. The rivets provide the a raised contact on opposite sides of the thin polymer sheet. The metal rivets provide the interconnection between the integrated circuit device and the substrate with fan out wiring. The geometry of the metal rivets provides a means of limiting the penetration of the probe tip into the solder balls on the integrated circuit device. The probes are separate from the wiring on the substrate and must be aligned to the contact pads on the substrate and the solder balls on the integrated circuit device. The probes are fabricated using gray scale photolithography processes and a single probe cannot be replaced or repaired.